(a) Field of the Invention
The present invention relates to an apparatus and a method of driving a liquid crystal display.
(b) Description of Related Art
A flat panel display such as a liquid crystal display (LCD) and an organic light emitting display (OLED) includes a display panel, a plurality of drivers for driving the display panel, and a controller for controlling the drivers.
An LCD includes two panels having pixel electrodes and a common electrode and a liquid crystal (LC) layer with dielectric anisotropy, which is interposed between the two panels. The pixel electrodes are arranged in a matrix, connected to switching elements such as thin film transistors (TFTs), and supplied with data voltages through the switching elements. The common electrode covers entire surface of one of the two panels and is supplied with a common voltage. The pixel electrode, the common electrode, and the LC layer form a LC capacitor in circuital view, which is a basic element of a pixel along with the switching element connected thereto.
In the LCD, the two electrodes supplied with the voltages generate electric field in the LC layer, and the transmittance of light passing through the LC layer is adjusted by controlling the strength of the electric field, thereby obtaining desired images. In order to prevent image deterioration due to the unidirectional electric field, polarity of the data voltages with respect to the common voltage is reversed every frame, every row, or every dot.
The display device receives digital input image data for red, green, and blue colors from an external graphics source. A signal controller of the display device appropriately processes the input image data and supplies the processed image data to a data driver. The data driver converts the digital image data into analog data voltages and applies the data voltages to the pixels.
The bit number of the input image data from the graphics source may not be equal to that of the image data capable of being processed in the data driver. For example, a data driver capable of processing only 6-bit data is commonly used for reducing the manufacturing cost although the bit number of the input image data is eight.
In order to convert the 8-bit image data into the 6-bit image data capable of being processed in the data driver, it is proposed that frame rate control (FRC) should be applied for use in the display device.
FRC represents high-bit data as low-bit data and their temporal and spatial arrangements. For FRC, the signal controller modifies a high-bit input data in a frame for a pixel into a low-bit data depending on the position of the pixel and the serial number of the frame. A pattern containing the modification data as function of the position of the pixel and the serial number of the frame, which is stored in a memory such as a frame memory, is called FRC pattern.
Such FRC pattern is determined so that it may not generate stripes or flickering on the display device due to the difference in the data voltages or due to the polarity of the data voltages.